Nikon Shutter priority not selecting the best Aperture

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OneMrEd

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When I’m in shutter priority with the shutter set 1/800 of the second the camera is selecting sub optimal (for image quality in my opinion) settings. For example, it selected F11 and ISO 8000. Why would it have not selected a lower aperture to minimize raising the ISO. I have many examples of this.

I know that I could just put it in manual mode (with auto ISO) and work around this issue but I'm questioning and trying to understand why Nikon would've programmed the camera to select the settings it does in shutter priority. In my mind, when you're in shutter priority you're in essence telling the camera, do what you will to the aperture to allow the correct exposure. And, the combination of F8 and ISO 1800 just makes no sense. The camera should have widened the aperture to 5.6 ( the widest at 400 mm on this lens) so that it could have set a lower ISO value.

My configuration:
  • Z9 with firmware 5.0
  • Nikkor z 100-400 4.5 to 5.6
  • auto ISO turned on with base sensitivity set at 64
  • 30 FPS (it will do the same at 20 fps)
  • JPEG
 
You are in auto ISO? I don't know then, but smaller than f11 can lead to diffraction softening, so maybe it's not a bad auto setting. Might be better than 4000 at f16? Full manual with auto iso is like aperture and shutter priority, roll your own and you don't have to second guess the auto settings.
 
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The camera will select an aperture and ISO which will provide for proper exposure given lighting conditions, the metering mode you selected, and the shutter speed you selected. If you’d prefer a lower ISO than what the camera selected you have two choices:

1) Limit the ISO by specifying a maximum ISO using ISO sensitivity settings. The camera will attempt to accommodate that by varying aperture. Realize that, depending on the max ISO you specify, some lighting conditions may require a larger aperture than is available on the lens.

2) Shoot in full manual or manual with auto ISO.

Generally speaking, I use option 2. I rarely shoot using shutter priority.
 
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What is the best aperture? The camera doesn't know your intent while shooting an image. When using shutter priority and auto ISO the camera wants to give you a little DOF so it is closing down the aperture a little. The camera just doesn't know if you are shooting a subject that will work with a narrow DOF or you might need a little DOF. That is why I use manual with auto ISO, I can decide how fast of a shutter speed I need and what aperture will work best for the subject I am shooting, and let the camera adjust the ISO.

I also think that when two auto features are enabled the camera will attempt to balance them out. If your max ISO is set at 25600 then the camera thinks you are willing to shoot that high so 8000 still gives you more than 1 fstop below your max.

If shooting aperture priority with auto ISO, the camera can recognize what lens is being used and maintain a shutter speed fast enough to give a stable image based on focal length.
 
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bleirer said:
You are in auto ISO? I don't know then, but smaller than f11 can lead to diffraction softening, so maybe it's not a bad auto setting. Might be better than 4000 at f16? Full manual with auto iso is like aperture and shutter priority, roll your own and you don't have to second guess the auto settings.
Click to expand...
Yes, I'm in auto ISO with a base of 64
 
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MartyD said:
What is the best aperture? The camera doesn't know your intent while shooting an image. When using shutter priority and auto ISO the camera wants to give you a little DOF so it is closing down the aperture a little. The camera just doesn't know if you are shooting a subject that will work with a narrow DOF or you might need a little DOF. That is why I use manual with auto ISO, I can decide how fast of a shutter speed I need and what aperture will work best for the subject I am shooting, and let the camera adjust the ISO.

I also think that when two auto features are enabled the camera will attempt to balance them out. If your max ISO is set at 25600 then the camera thinks you are willing to shoot that high so 8000 still gives you more than 1 fstop below your max.

If shooting aperture priority with auto ISO, the camera can recognize what lens is being used and maintain a shutter speed fast enough to give a stable image based on focal length.
Click to expand...
In my opinion the best aperture is the widest aperture when you're in shutter priority mode. That will keep the ISO at the lowest possible amount which is what you should always aim to do to get the cleanest image
 
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tclune said:
There used to be a rule of thumb that lenses were generally at their sharpest two stops below maximum aperture. Perhaps the algorithm is working from that? Just a thought.
Click to expand...
If it chose a higher aperture number consistently I would agree with this logic but it's not. Thanks for the idea.
 
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OneMrEd said:
In my opinion the best aperture is the widest aperture when you're in shutter priority mode. That will keep the ISO at the lowest possible amount which is what you should always aim to do to get the cleanest damage
Click to expand...
When using shutter priority there are lighting conditions in which even the widest aperture will not provide for proper exposure given your selected shutter speed and a “low” ISO. In that case an “unacceptably high” ISO may be required.
 
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As mentioned above, I would not use two "auto" settings.....in your situation you have both the aperture and ISO being determined by the camera. I use Auto ISO a lot, but in manual mode. I want to control both shutter speed and aperture. So I only let the camera decide on the ISO. If I don't like the exposure I adjust the exposure using the exposure compensation button on the top right of the camera.

I do this because the camera cannot think. The camera does not know if I want to shoot wide open or close down a bit to increase the DOF. It does not know if I want a high key or low key image. It does not know if I want to protect the whites - or the blacks.
 
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Yeah, try turning off Auto ISO. It's already determining ISO with Shutter Priority, so I suspect having Auto ISO on, too, is "confusing" the camera.
 
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Woodyg3 said:
Yeah, try turning off Auto ISO. It's already determining ISO with Shutter Priority, so I suspect having Auto ISO on, too, is "confusing" the camera.
Click to expand...
probably a point without distinction, but the confusion will be on the human’s part, not the camera

there are a variety of settings that help control the behavior in these cases, and it’s easy to mess it up. but theoretically you can control the behavior
 
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@OneMrEd

If you want bigger apertures and use auto ISO + shutter priority you need to limit the ISO peak so the aperture stays wide or use exposure compensation which will raise the shutter speed. Both of which you risk not getting the right exposure. Most people use full manual mode with auto ISO.

As others have said, cameras are dumb. They don't know what you want. All they know is what will give the right exposure and a good depth of field in a semi auto mode. Using two semi auto modes is probably messing with it too.
 
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Not sure what subject(s) you are shooting, but when shooting sports I normally shoot in Aperture mode and shoot wide open. Following that I select a minimum shutter speed along with auto ISO, setting a top speed (called Auto ISO). There are times when I shoot on manual, Auto ISO and lock in the highest acceptable ISO, accepting (and repairing) any exposure issues in post. My not work for you, but it's what I do, without all the details. Best of luck.
 
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OneMrEd said:
When I’m in shutter priority with the shutter set 1/800 of the second the camera is selecting sub optimal (for image quality in my opinion) settings. For example, it selected F11 and ISO 8000. Why would it have not selected a lower aperture to minimize raising the ISO. I have many examples of this.

I know that I could just put it in manual mode (with auto ISO) and work around this issue but I'm questioning and trying to understand why Nikon would've programmed the camera to select the settings it does in shutter priority. In my mind, when you're in shutter priority you're in essence telling the camera, do what you will to the aperture to allow the correct exposure. And, the combination of F8 and ISO 1800 just makes no sense. The camera should have widened the aperture to 5.6 ( the widest at 400 mm on this lens) so that it could have set a lower ISO value.

My configuration:
  • Z9 with firmware 5.0
  • Nikkor z 100-400 4.5 to 5.6
  • auto ISO turned on with base sensitivity set at 64
  • 30 FPS (it will do the same at 20 fps)
  • JPEG
Click to expand...
What are you taking pictures of? I can't get a clean image of a songbird handheld at 1/800. In S mode, I'm likely at 1/3200. Most recently shot in M mode and varied aperture a little, with quite a few keepers a stop or two down from the max. Also shoot auto ISO.
 
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